Java DOM XML Parser

2024-03-19 12:38
文章标签 java xml parser dom

本文主要是介绍Java DOM XML Parser，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

DOM parser parses the entire XML document and loads it into memory; then models it in a “TREE” structure for easy traversal or manipulation.

In short, it turns a XML file into DOM or Tree structure, and you have to traverse a node by node to get what you want.

Warning
DOM Parser is slow and consumes a lot of memory when it loads an XML document which contains a lot of data. Please consider SAX parser as solution for it, SAX is faster than DOM and use less memory.

1.0 How to read XML file in Java

/Users/mkyong/staff.xml

<?xml version="1.0"?>
<company><staff id="1001"><firstname>yong</firstname><lastname>mook kim</lastname><nickname>mkyong</nickname><salary>100000</salary></staff><staff id="2001"><firstname>low</firstname><lastname>yin fong</lastname><nickname>fong fong</nickname><salary>200000</salary></staff>
</company>

ReadXMLFile.java

package com.mkyong.seo;import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import java.io.File;public class ReadXMLFile {public static void main(String argv[]) {try {File fXmlFile = new File("/Users/mkyong/staff.xml");DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();Document doc = dBuilder.parse(fXmlFile);//optional, but recommended//read this - http://stackoverflow.com/questions/13786607/normalization-in-dom-parsing-with-java-how-does-it-workdoc.getDocumentElement().normalize();System.out.println("Root element :" + doc.getDocumentElement().getNodeName());NodeList nList = doc.getElementsByTagName("staff");System.out.println("----------------------------");for (int temp = 0; temp < nList.getLength(); temp++) {Node nNode = nList.item(temp);System.out.println("\nCurrent Element :" + nNode.getNodeName());if (nNode.getNodeType() == Node.ELEMENT_NODE) {Element eElement = (Element) nNode;System.out.println("Staff id : " + eElement.getAttribute("id"));System.out.println("First Name : " + eElement.getElementsByTagName("firstname").item(0).getTextContent());System.out.println("Last Name : " + eElement.getElementsByTagName("lastname").item(0).getTextContent());System.out.println("Nick Name : " + eElement.getElementsByTagName("nickname").item(0).getTextContent());System.out.println("Salary : " + eElement.getElementsByTagName("salary").item(0).getTextContent());}}} catch (Exception e) {e.printStackTrace();}}}

Result:

Root element :company
----------------------------Current Element :staff
Staff id : 1001
First Name : yong
Last Name : mook kim
Nick Name : mkyong
Salary : 100000Current Element :staff
Staff id : 2001
First Name : low
Last Name : yin fong
Nick Name : fong fong
Salary : 200000

Looping the Node
ReadXMLFile2.java

package com.mkyong.seo;import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;public class ReadXMLFile2 {public static void main(String[] args) {try {File file = new File("/Users/mkyong/staff.xml");DocumentBuilder dBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();Document doc = dBuilder.parse(file);System.out.println("Root element :" + doc.getDocumentElement().getNodeName());if (doc.hasChildNodes()) {printNote(doc.getChildNodes());}} catch (Exception e) {System.out.println(e.getMessage());}}private static void printNote(NodeList nodeList) {for (int count = 0; count < nodeList.getLength(); count++) {Node tempNode = nodeList.item(count);// make sure it's element node.if (tempNode.getNodeType() == Node.ELEMENT_NODE) {// get node name and valueSystem.out.println("\nNode Name =" + tempNode.getNodeName() + " [OPEN]");System.out.println("Node Value =" + tempNode.getTextContent());if (tempNode.hasAttributes()) {// get attributes names and valuesNamedNodeMap nodeMap = tempNode.getAttributes();for (int i = 0; i < nodeMap.getLength(); i++) {Node node = nodeMap.item(i);System.out.println("attr name : " + node.getNodeName());System.out.println("attr value : " + node.getNodeValue());}}if (tempNode.hasChildNodes()) {// loop again if has child nodesprintNote(tempNode.getChildNodes());}System.out.println("Node Name =" + tempNode.getNodeName() + " [CLOSE]");}}}
}
2.0 How to modify XML file in Java

修改前xml file
file.xml

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<company><staff id="1"><firstname>yong</firstname><lastname>mook kim</lastname><nickname>mkyong</nickname><salary>100000</salary></staff>
</company>

修改后xml

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<company><staff id="2"><lastname>mook kim</lastname><nickname>mkyong</nickname><salary>2000000</salary><age>28</age></staff>
</company>

ModifyXMLFile .java修改xml

import java.io.File;
import java.io.IOException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;public class ModifyXMLFile {public static void main(String argv[]) {try {String filepath = "c:\\file.xml";DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();DocumentBuilder docBuilder = docFactory.newDocumentBuilder();Document doc = docBuilder.parse(filepath);// Get the root elementNode company = doc.getFirstChild();// Get the staff element , it may not working if tag has spaces, or// whatever weird characters in front...it's better to use// getElementsByTagName() to get it directly.// Node staff = company.getFirstChild();// Get the staff element by tag name directlyNode staff = doc.getElementsByTagName("staff").item(0);// update staff attributeNamedNodeMap attr = staff.getAttributes();Node nodeAttr = attr.getNamedItem("id");nodeAttr.setTextContent("2");// append a new node to staffElement age = doc.createElement("age");age.appendChild(doc.createTextNode("28"));staff.appendChild(age);// loop the staff child nodeNodeList list = staff.getChildNodes();for (int i = 0; i < list.getLength(); i++) {Node node = list.item(i);// get the salary element, and update the valueif ("salary".equals(node.getNodeName())) {node.setTextContent("2000000");}//remove firstnameif ("firstname".equals(node.getNodeName())) {staff.removeChild(node);}}// write the content into xml fileTransformerFactory transformerFactory = TransformerFactory.newInstance();Transformer transformer = transformerFactory.newTransformer();DOMSource source = new DOMSource(doc);StreamResult result = new StreamResult(new File(filepath));transformer.transform(source, result);System.out.println("Done");} catch (ParserConfigurationException pce) {pce.printStackTrace();} catch (TransformerException tfe) {tfe.printStackTrace();} catch (IOException ioe) {ioe.printStackTrace();} catch (SAXException sae) {sae.printStackTrace();}}
}
3.0 How to create XML file in Java

要生成的xml file.xml

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<company><staff id="1"><firstname>yong</firstname><lastname>mook kim</lastname><nickname>mkyong</nickname><salary>100000</salary></staff>
</company>

WriteXMLFile .java

package com.mkyong.core;import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;public class WriteXMLFile {public static void main(String argv[]) {try {DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();DocumentBuilder docBuilder = docFactory.newDocumentBuilder();// root elementsDocument doc = docBuilder.newDocument();Element rootElement = doc.createElement("company");doc.appendChild(rootElement);// staff elementsElement staff = doc.createElement("Staff");rootElement.appendChild(staff);// set attribute to staff elementAttr attr = doc.createAttribute("id");attr.setValue("1");staff.setAttributeNode(attr);// shorten way// staff.setAttribute("id", "1");// firstname elementsElement firstname = doc.createElement("firstname");firstname.appendChild(doc.createTextNode("yong"));staff.appendChild(firstname);// lastname elementsElement lastname = doc.createElement("lastname");lastname.appendChild(doc.createTextNode("mook kim"));staff.appendChild(lastname);// nickname elementsElement nickname = doc.createElement("nickname");nickname.appendChild(doc.createTextNode("mkyong"));staff.appendChild(nickname);// salary elementsElement salary = doc.createElement("salary");salary.appendChild(doc.createTextNode("100000"));staff.appendChild(salary);// write the content into xml fileTransformerFactory transformerFactory = TransformerFactory.newInstance();Transformer transformer = transformerFactory.newTransformer();DOMSource source = new DOMSource(doc);StreamResult result = new StreamResult(new File("C:\\file.xml"));// Output to console for testing// StreamResult result = new StreamResult(System.out);transformer.transform(source, result);System.out.println("File saved!");} catch (ParserConfigurationException pce) {pce.printStackTrace();} catch (TransformerException tfe) {tfe.printStackTrace();}}
}
4.0 How to count XML Elements in Java

file.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<company><staff id="1"><firstname>yong</firstname><lastname>mook kim</lastname><nickname>mkyong</nickname><salary>2000000</salary><age>29</age></staff><staff id="2"><firstname>low</firstname><lastname>yin fong</lastname><nickname>fong fong</nickname><salary>1000000</salary></staff><staff id="3"><firstname>Ali</firstname><lastname>Baba</lastname><nickname>Alibaba</nickname><salary>199000</salary><age>40</age></staff>
</company>

CountXMLElement.java 

import java.io.IOException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;public class CountXMLElement {public static void main(String argv[]) {try {String filepath = "c:\\file.xml";DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();DocumentBuilder docBuilder = docFactory.newDocumentBuilder();Document doc = docBuilder.parse(filepath);NodeList list = doc.getElementsByTagName("staff");System.out.println("Total of elements : " + list.getLength());} catch (ParserConfigurationException pce) {pce.printStackTrace();} catch (IOException ioe) {ioe.printStackTrace();} catch (SAXException sae) {sae.printStackTrace();}}
}
5.0 解析网络xml

AlexaSEO.java

package com.mkyong.seo;import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;public class AlexaSEO {public static void main(String[] args) {AlexaSEO obj = new AlexaSEO();System.out.println("Ranking : " + obj.getAlexaRanking("mkyong.com"));}public int getAlexaRanking(String domain) {int result = 0;String url = "http://data.alexa.com/data?cli=10&url=" + domain;try {URLConnection conn = new URL(url).openConnection();InputStream is = conn.getInputStream();DocumentBuilder dBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();Document doc = dBuilder.parse(is);Element element = doc.getDocumentElement();NodeList nodeList = element.getElementsByTagName("POPULARITY");if (nodeList.getLength() > 0) {Element elementAttribute = (Element) nodeList.item(0);String ranking = elementAttribute.getAttribute("TEXT");if(!"".equals(ranking)){result = Integer.valueOf(ranking);}}} catch (Exception e) {System.out.println(e.getMessage());}return result;}
}

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